Fix walsender to exit promptly if client requests shutdown.
It's possible for WalSndWaitForWal to be asked to wait for WAL that doesn't
exist yet. That's fine, in fact it's the normal situation if we're caught
up; but when the client requests shutdown we should not keep waiting.
The previous coding could wait indefinitely if the source server was idle.
In passing, improve the rather weak comments in this area, and slightly
rearrange some related code for better readability.
Back-patch to 9.4 where this code was introduced.
Discussion: https://postgr.es/m/14154.1498781234@sss.pgh.pa.us
Branch
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REL9_5_STABLE
Details
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https://git.postgresql.org/pg/commitdiff/446914f6b69a81d1306d0deeadc1eb2e8a02c264
Modified Files
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src/backend/replication/walsender.c | 48 ++++++++++++++++++++++++-------------
1 file changed, 31 insertions(+), 17 deletions(-)